1. Field of the Invention
The present invention relates to a structure allowing for detection of a load applied to a vehicle seat. In particular, the invention is directed to such load detection structure for use in a slidable type of vehicle seat, or the so-called xe2x80x9csliding seatxe2x80x9d which are equipped with a pair of spaced-apart slide rails for allowing the seat to move in fore-and-aft direction, wherein a load detection element is mounted between the seat and the two slide rails.
2. Description of Prior Art
There have been known a passenger detection system for detecting the presence and absence of a passenger or driver in a seat of vehicle in advance before actuating or stopping the associated mechanical elements to automatically control various functions and mechanisms built in the seat.
Normally, the passenger detection system employs various sensors (e.g. a pressure sensitive element) which detect the weight of a passenger on a seat and emit a signal to electronic control systems for automatic control of various mechanical elements related to the seat. Most of the sensors are of a simple structure which can only sense the presence and absence of passenger on a seat, but the recent high-tech control technology inevitably requires that the sensors should further detect whether the passenger is an adult or a child as with an air bag control system for instance.
To meet the demand, there have been proposed sensor systems for numerically detecting the weight of passenger or a corresponding load applied to the seat, determining whether the passenger is adult or child, according to a numerical data obtained, and then controlling and adjusting the associated mechanical elements to optimal conditions suited for the adult or child (e.g. controlling air bag), as disclosed from the Japanese Laid-Open Patent Publications No. 11-304579 for instance. As known form such publication, a load applied to the seat is detected by load sensor which includes one mode of sensor for directly sensing the load or another mode of sensor using a deformable material which directly receives the load and a strain gauge for detecting a degree of deformation of that deformable material, to thereby detect a precise load applied to the seat. In any case, the sensors directly receives a load applied to the seat and therefore it is required that a load detection system should be provided with a high sensitivity to precisely detect a weight of any person in a wide range including children and adults, and further the load detection system be provided with a high protection against an overload due to such an emergency accident as a collision.
As widely known, most of vehicle or automotive seats are equipped with a pair of spaced-apart slide rails (or seat slide device) at the bottom side thereof, constituting what is called xe2x80x9csliding seatxe2x80x9d which is slidable via the two slide rails in the fore-and-aft direction. It is a main or common practice to mount the foregoing passenger detection system to such slide rails. According to the Japanese Pub. No. 11-304579 stated above, the sensors and the associated mechanisms have to be mounted either upon or below the two slide rails. In particular, if those sensors and mechanism are mounted below the slide rails, it will be necessary to provide a special space below the slide rails, in which to accommodate them. As a result, the seat on the whole is raised to an undesired level resulting in heightening a seating level where a seat occupant sits on the seat.
In view of the above-stated drawbacks, it is therefore a primary purpose of the present invention to provide an improved load detection structure which can be installed in the seat without increasing the height of the seat.
In order to achieve such purpose, the load detection structure of the present invention is basically comprised of:
a load detection means for detecting a load applied to a vehicle seat, the load detection means including:
a block element of a generally oblong shape having a rigid yet resiliently deflectable property that tends to recover into its original shape, the block element having a movable portion; a securing portion; and a deflectable area defined between the movable portion and securing portion, wherein the movable portion is formed with a horizontally elongated hole therein; and
a strain gauge means provided on the deflectable area;
the load detection means being arranged laterally of the upper rail such that the securing portion of block element is fixedly secured to the lateral side of upper rail;
a vertically elongated hole formed in the lateral wall of upper rail;
a connecting pin; and
a pair of spaced-apart link pieces so provided below the seat as to extend downwardly therefrom, with such an arrangement that the pair of spaced-apart link pieces being disposed symmetrically relative to and on the opposite sides of both upper rail and movable portion of block element,
wherein one of the pair of spaced-apart link pieces being connected with another of the pair of spaced-apart link pieces in such a manner that said connecting pin is secured in the hole of movable portion while being slidably inserted through the vertically elongated hole, and
wherein the pair of spaced-apart link pieces are supported by the movable portion of block element so that a load applied to the seat is transmitted to the movable portion, thereby causing deflection of the delectable area of block element, in response to which, the strain gauge means detects an amount of the deflection.
Accordingly, since the load detection means is located at the lateral side of the upper rail, any other element for supporting the load detection means is not interposed between the seat and two slide rail devises, thereby avoiding undesired increase in height of the seat.
In one aspect of the present invention, the load detection structure may further includes a pair of first and second limit pieces, which are respectively defined at a point adjacent to one side of the movable portion of block element with a first gap therebetween and at another point adjacent to another side of the movable portion with a second gap therebetween, the pair of first and second limit elements being adapted to limit the vertical movement of the movable portion of block element, while allowing such vertical movement within a limited space including the first and second gaps.
In another aspect of the invention, the load detection structure may include a limiter member of generally channel cross-section having first and second horizontal portions formed therein and being so configured as to cover the block element, and the foregoing first and second limit pieces may respectively be formed integrally in said first and second horizontal portions, and wherein the limiter member is securely connected with the lateral side of upper rail, covering the block element.
In yet another aspect of the invention, the load detection structure may further include a link assembly comprising four spaced-apart link elements in a generally rectangular shape having four corner portions, and such link assembly may be provided between the seat and the pair of spaced-apart slide rail devices, with such an arrangement that the load detection means are connected integrally with the four corner portions of the link assembly, while being disposed at one end portion of each of the two slide rail devices and disposed also at another opposite end portion of each of the two slide rail devices.
Other features and advantages will become apparent from reading of the description hereinafter, with reference to the annexed drawings.